Re: [Boost-bugs] [Boost C++ Libraries] #8652: boost::geometry::intersection fails for triangle-triangle intersection

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #8652: boost::geometry::intersection fails for triangle-triangle intersection
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-08-27 20:57:06

#8652: boost::geometry::intersection fails for triangle-triangle intersection
-------------------------------+---------------------------
  Reporter:  flo@…             |      Owner:  barendgehrels
      Type:  Bugs              |     Status:  closed
 Milestone:  To Be Determined  |  Component:  geometry
   Version:  Boost 1.53.0      |   Severity:  Problem
Resolution:  fixed             |   Keywords:
-------------------------------+---------------------------
Changes (by barendgehrels):

 * status:  new => closed
 * resolution:   => fixed

Comment:

 The boundaries of double are reached by using coordinates as specified.
 This results in rounding errors and imprecise results.

 The extra point which was generated is fixed in commit 85451 (will be
 released in Boost 1.55).

 The output was:
 POLYGON((0.05 0.02,0.05 -2.77556e-17,0.02 -2.77556e-17,0.05 0.02))
 Area: 0.0003

 The new output is:
 POLYGON((0.05 0.02,0.05 0,0.02 -2.77556e-17,0.05 0.02))
 Area: 0.0003

 So still not as your expectation but it comes close.

 If you use "long double" (better suited for cases like this), the output
 is correct:The computed intersection is:
 POLYGON((0.05 0.02,0.05 0,0.02 0,0.05 0.02))
 Area: 0.0003

 (I changed output to WKT and added area in your testprogram).

 I will add a testcase for this ticket to avoid future regressions.

 SQL Server gives:
 POLYGON ((0.019999999552965164 0, 0.049999999813735485 0,
 0.049999999813735485 0.019999999552965164, 0.019999999552965164 0))
 Area: 0.000299999995902181

 I did not check your integer-sample, if that is a separate problem, please
 create a separate ticket.

 Thanks for your report.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8652#comment:4>
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